seccomp_init, seccomp_reset - Initialize the seccomp filter state
#include <seccomp.h>
typedef void * scmp_filter_ctx;
scmp_filter_ctx seccomp_init(uint32_t def_action);
int seccomp_reset(scmp_filter_ctx ctx, uint32_t def_action);
Link with -lseccomp.
The
seccomp_init() and
seccomp_reset() functions (re)initialize
the internal seccomp filter state, prepares it for use, and sets the default
action based on the
def_action parameter. The
seccomp_init()
function must be called before any other libseccomp functions as the rest of
the library API will fail if the filter context is not initialized properly.
The
seccomp_reset() function releases the existing filter context state
before reinitializing it and can only be called after a call to
seccomp_init() has succeeded. If
seccomp_reset() is called with
a NULL filter, it resets the library's global task state, including any
notification file descriptors retrieved by
seccomp_notify_fd(3).
Normally this is not needed, but it may be required to continue using the
library after a
fork() or
clone() call to ensure the API level
and user notification state is properly reset.
When the caller is finished configuring the seccomp filter and has loaded it
into the kernel, the caller should call
seccomp_release(3) to release
all of the filter context state.
Valid
def_action values are as follows:
- SCMP_ACT_KILL
- The thread will be terminated by the kernel with SIGSYS
when it calls a syscall that does not match any of the configured seccomp
filter rules. The thread will not be able to catch the signal.
- SCMP_ACT_KILL_PROCESS
- The entire process will be terminated by the kernel with
SIGSYS when it calls a syscall that does not match any of the configured
seccomp filter rules.
- SCMP_ACT_TRAP
- The thread will be sent a SIGSYS signal when it calls a
syscall that does not match any of the configured seccomp filter rules. It
may catch this and change its behavior accordingly. When using SA_SIGINFO
with sigaction(2), si_code will be set to SYS_SECCOMP, si_syscall
will be set to the syscall that failed the rules, and si_arch will be set
to the AUDIT_ARCH for the active ABI.
- SCMP_ACT_ERRNO(uint16_t errno)
- The thread will receive a return value of errno when
it calls a syscall that does not match any of the configured seccomp
filter rules.
- SCMP_ACT_TRACE(uint16_t msg_num)
- If the thread is being traced and the tracing process
specified the PTRACE_O_TRACESECCOMP option in the call to
ptrace(2), the tracing process will be notified, via
PTRACE_EVENT_SECCOMP, and the value provided in msg_num can
be retrieved using the PTRACE_GETEVENTMSG option.
- SCMP_ACT_LOG
- The seccomp filter will have no effect on the thread
calling the syscall if it does not match any of the configured seccomp
filter rules but the syscall will be logged.
- SCMP_ACT_ALLOW
- The seccomp filter will have no effect on the thread
calling the syscall if it does not match any of the configured seccomp
filter rules.
The
seccomp_init() function returns a filter context on success, NULL on
failure. The
seccomp_reset() function returns zero on success or one of
the following error codes on failure:
- -EINVAL
- Invalid input, either the context or action is
invalid.
- -ENOMEM
- The library was unable to allocate enough memory.
#include <seccomp.h>
int main(int argc, char *argv[])
{
int rc = -1;
scmp_filter_ctx ctx;
ctx = seccomp_init(SCMP_ACT_KILL);
if (ctx == NULL)
goto out;
/* ... */
rc = seccomp_reset(ctx, SCMP_ACT_KILL);
if (rc < 0)
goto out;
/* ... */
out:
seccomp_release(ctx);
return -rc;
}
While the seccomp filter can be generated independent of the kernel, kernel
support is required to load and enforce the seccomp filter generated by
libseccomp.
The libseccomp project site, with more information and the source code
repository, can be found at
https://github.com/seccomp/libseccomp. This tool,
as well as the libseccomp library, is currently under development, please
report any bugs at the project site or directly to the author.
Paul Moore <
[email protected]>
seccomp_release(3)